The entire disclosure of Japanese Patent Application No. Hei 10-14352 filed on Jan. 27, 1998 including specification, claims, drawings and summary are incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly to a technique for improving the component separating function of a semiconductor device.
2. Description of the Related Art
MOS type field effect transistors (Metal Oxide Semiconductor Field Effect Transistor) are known as semiconductor components. FIG. 8 is a conceptual figure of a flat structure of a semiconductor device comprising conventional MOS type field effect transistors (referred to at times hereafter simply as xe2x80x9ctransistorxe2x80x9d). FIG. 9 shows cross-section 9xe2x80x949 of FIG. 8.
As shown in FIG. 9, a transistor 12 is formed within this semiconductor device. The transistor 12 comprises a channel forming region CH which is sandwiched between source S1 and drain D1 (see FIG. 8).
A gate electrode 22 is formed on the channel forming region CH via a gate oxide film 20. An interlayer film 24 is formed on the gate electrode 22. An aluminum wiring 28 is formed on the interlayer film 24. The gate electrode 22 and the aluminum wiring 28 are connected via a contact hole 26 which is formed in the interlayer film 24.
Another transistor 14 is formed on the semiconductor device separately from the transistor 12 via a field oxide film 18 for component separation. Thus, by interposing the field oxide film 18 between the two transistors 12 and 14, it is possible to separate the transistors electrically.
However, such conventional semiconductor devices have the following type of problems. As shown in FIG. 9, the contact hole 26 for connecting the gate electrode 22 and the aluminum wiring 28 is formed on the field oxide film 18. Therefore, part of the gate electrode 22 of the transistor 12 is placed directly on top of the field oxide film 18.
Thus, when a voltage is applied to the gate electrode 22, there is a possibility of the surface of semiconductor layer 16 (the part shown by the xe2x80x9cxxe2x80x9d mark in the figure) directly below the field oxide film 18 being inverted. There is a particularly high risk for this with high withstand voltage transistors for which a high voltage is applied to the gate electrode 22. If the surface of the semiconductor layer 16 beneath the field oxide film 18 is inverted, the inverted portion will not function as a component separating region.
To electrically separate the transistor 12 and the transistor 14 to avoid this situation, a sufficiently large length L1 of the non-inverted part can be secured. However, with this method, the overall length L2 of the field oxide film 18 becomes long, so the layout space for the transistor 12 and the transistor 14 becomes large. This leads to a reduction in the degree of integration of the semiconductor device.
Another method that can be considered to avoid the problem described above is making the film thickness of the field oxide film 18 thick. However, if the overall length L2 of the field oxide film 18 is left as is and the film thickness is increased, the incline angle of the area near the edge (bird""s beak area) 18a of the field oxide film 18 becomes large, and the degree of concentration of the electrical field for the edge area 18a becomes larger. This makes it impossible to obtain the desired withstand voltage.
Also, if the film thickness of the field oxide film 18 is increased, a greater time is required for forming the field oxide film 18, so production efficiency is lowered, and production costs are increased.
As a further method for avoiding the problems described above, we can consider a method of increasing the density of channel stop ions implanted into the surface of the semiconductor layer 16 which is under the field oxide film 18. However, if the density of the channel stop ions is increased, there is a decrease in the withstand voltage.
An object of the present invention is to provide a semiconductor device that solves these types of problems and that can separate components easily.
In accordance with characteristics of the present invention, there is provided a semiconductor device comprising:
a base semiconductor layer,
an insulation film for separating components formed on the base semiconductor layer, and
a semiconductor component which is formed on the base semiconductor layer in a component forming region separated by the insulation film for separating components, the semiconductor component having a first conductive layer,
wherein the semiconductor device comprises:
an interlayer insulation film placed on the insulation film for separating components and the first conductive layer, and
a second conductive layer placed on the interlayer insulation film,
wherein the first conductive layer is substantially formed only within the component forming region, and
wherein the first conductive layer and the second conductive layer are substantially connected only within the component forming region.
In accordance with characteristics of the present invention, there is provided a wiring method for a semiconductor device comprising an insulation film for separating components formed on a base semiconductor layer, wherein wiring is substantially performed using a first wiring layer only within a component forming region separated by the insulation film for separating components;
wiring is performed using a second wiring layer on an interlayer insulation film formed on the insulation film for separating components and the first wiring layer;
the first wiring layer and the second wiring layer are substantially connected only within the component forming region.
The characteristics of the present invention are broadly indicated as noted above, but the structure, contents, object, and features will be clearer through reference to the figures and according to the following disclosure.